Solar DC input for charging Cybertruck from trailer panels

[ajdelange]

Incroyable!

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[CappyJax]

Spending a 1/3rd of a year exploring an entire country without spending a time on energy would be the whole damn point! It would be awesome!

 

[ajdelange]

As I am writing this I am charging a battery pack with arrays that produce 18 V (presumably also at the PPP).

As the noise level has gotten pretty high here I don't know if OP is still with us but a couple of additional thoughts might interest him. First is that I took some measurements this morning on the panel I mentioned in an earlier post. The panel is made by Jackery and rated "100W/18V". In today's bright sun (45 °N) it produces an open circuit voltage of 20.3 volts. When connected to a controller with MPP it is able to collect about 60 W and the voltage drops to 17.3V. When clouds roll in the output drops but even at the 2 watt level never goes below 17 V. Those familiar with PV cell IV curves will understand this.

The most important thing to OP in this is that practically speaking I'm not getting 100% of the rated power out of this panel and you will not either. Thus the range numbers I have given are optimistic. and your plan to do this on solar alone isn't very realistic. However, I had a look at PlugShare today and the charging opportunities up the Stuart, across on the Barkly, out on the Nulabor and all around the coasts aren't bad. Perhaps with a combination of charging at road houses etc and solar your trip might be feasible especially if time is unlimited.

 

[Crissa]

...And if you were using a maximum power point tracking (MPPT) system instead of a pulse-width modulation or simple point conversion you'd wire additional panels in series instead of parallel and then say you have four they'd peak at 82V instead of 20V.

The reason most panels are wired to lower voltage is to make them safer to install. But if you already have high-voltage requirements, say in an electric truck that supports DC fast charging, then there's no reason not to run them as high voltage low-amperage arrays.

-Crissa

 

[CappyJax]

...And if you were using a maximum power point tracking (MPPT) system instead of a pulse-width modulation or simple point conversion you'd wire additional panels in series instead of parallel and then say you have four they'd peak at 82V instead of 20V.

The reason most panels are wired to lower voltage is to make them safer to install. But if you already have high-voltage requirements, say in an electric truck that supports DC fast charging, then there's no reason not to run them as high voltage low-amperage arrays.

-Crissa

Yes, a 20' x 8.5' trailer with the roof covered in solar panels could produce as much as 340V. But it would be cool if Tesla were to allow for the battery pack to change from series to parallel so charging could be in the 26V range. I think Rivian has a patent on this though. They are suppose to allow for their pack to split into two parallel dropping the charging voltage from 950V to 450V.

I wonder how the semi charging works. Are there four 900V packs that are charged individually?

 

[Crissa]

The Semi charges their packs independently, yes.

Anyhow, as I was saying, it's just a matter of how you align the cells. The panels only produce low voltage because they're designed to. They could have the cells arranged in different patterns and be higher voltage.

They don't have to - and in fact won't - use pre-fabbed panels for the tonneau cover solar.

-Crissa

 

[hridge2020]

Here you go.. on the go.. sun power source

Even Arnold says..

 

[ajdelange]

Looks really cool (my wife wants a couple for our yard - "The return of the West Virginia state flower" she says) but keep in mind that it is very probably connected to Skynet and we don't want to mess with that!

In any case we note with interest that the company's website does not have one single number on it (except for a phone number) so we have to guess. It appears to be about 4 m in diameter and so would have a collection area of 12.6 m^2 which would collect 12.6 kW in full sun. With efficiency of 25% that would yield 3.2 kWh per hour of equivalent full sun which will be worth 8 miles to a CT. It apparently tracks so you could potentially get 6 or 7 hours equivalent full sun from it per day in a cloudless areas for 48 - 56 miles a day added to a CT. These are all rough numbers of course.

A couple of comments on solar systems are apparently in order. The architecture that seems to have been settled on, at least in residential installations, uses modest size panels (1.5 m^2; 300 + watts) each with it's own microinverter. These panels are, of course, series parallel configurations of solar cells (each of which produces half a volt) capable of delivering about 10 amps at around 35 volts DC in full sun (1 kW/m^2). The microinverters use PWM (pulse width modulation - a circuit is turned on for some fraction of a short period and the fraction of the period it is on controls the amount of power drawn or delivered to another part of the circuit) to convert the 33 volts from the panel to a higher DC voltage (around 350 - 400 V) and to do this so that the panel is loaded such that it always produces the maximum power it can whatever the level of insolation. (MPPT). PWM is then used again to convert the resulting DC to a voltage close to 240 VAC and the inverter wired to the building's 240V bus. The advantages of this are obvious - a single or a hundered microinverters can be attached to a residence's 240V electrical system. The panels are isolated from one another so that if one fails it does not drag the whole array performance down with it as is the case with the older systems that connected panels in series. If a meteorite goes through a panel the array output goes down by the amount that panel produced but not by more than that. The array isn't disabled by damage to one element of it. A perhaps less obvious advantage of this is that because a panel receiving less sun has no effect on other panels an array can effectively track the sun.

What I have described assumes the existence of a live 240 V bus which, of course, there is in a house but which there would not be in a trailer. The trailer would require functionality such as that of a Powerwall to supply the local bus and also to buffer up the collected energy. This would be required in any case as we are assuming no connection to the vehicle battery other than through the Level 2 charging port and this is a reasonable assumption for the time being.

It would, of course, be possible for Tesla to develop hardware and software to allow the connection of the individual micro controllers to the vehicle DC bus. Note that I now call them micro controllers rather than micro inverters because the inversion (second PWM stage) is no longer needed. The DC/DC converter that raises the panel's 33 V DC to near 400 VDC to charge the battery would be all that is needed. It is, of course, extremely unlikely that Tesla would do this.

 

[ldjessee]

Yeah, I watched someone saying that micro-inverters added too much overhead and cost and were not worth it, but my own experiments and others have shown that if you get ANY partial shadowing, it is well worth it... and if the system is mobile, you will most likely encounter situations that result in partial shadowing of one panel, but not several panels... or a variable amount of shadowing across panels, but if one is completely shadowed, then if in series and using a single inverter (or controller), then the whole string is not producing power.

 

[Crissa]

Well, it produces power at the lowest cell in the chain.

Monocrystalline panels suffer this the most, amorphous suffer shadows the least (but are the most awkward, being glass panels).

-Crissa

 

[markvan]

Thanks so much guys, sorry for the slow reply have been offgrid for while. I have read through all the posts and really appreciate the engineering minds input. I understood most of what was written and my take away is that running on solar alone is not very realistic, Unless I went with the Lightyear One, and that won't happen. As you've said there are many charging opportunities along the way which I should take advantage of. I think my dream may need to shift to being a little more pragmatic. Charging the CT at available opportunities (there will be even more available by the time it actually comes out). I can use the solar array on the trailer to power the fridge and campsite. Really appreciate the indepth explanations ajdelange and others helps me get a grasp on the strengths and limitations.

 

[jkashay]

Has anyone considered a Titan solar generator and 10x dokio 300 watt folding pane? The added weight seems negligible to the possible gains.

 

[ajdelange]

I have 500 Wh and 1000 Wh Jackery battery pack/inverters and find them quite useful for, for example, running an ARB fridge while the car is parked overnight as I don't want to run down the traction battery any more than the phantom drain already does and I'm not even sure the 12V outlets stay live after the car is turned off. They are also handier than the equivalent powered Honda camp generators in many applications.

I have also thought about the Yeti packs for short term home backup but they all suffer from the same shortcoming: no 120/120 biphase. I suppose I could kludge something with a transformer but that kind of flies in the face of the direction of the technology.

 

[jkashay]

I have 500 Wh and 1000 Wh Jackery battery pack/inverters and find them quite useful for, for example, running an ARB fridge while the car is parked overnight as I don't want to run down the traction battery any more than the phantom drain already does and I'm not even sure the 12V outlets stay live after the car is turned off. They are also handier than the equivalent powered Honda camp generators in many applications.

I have also thought about the Yeti packs for short term home backup but they all suffer from the same shortcoming: no 120/120 biphase. I suppose I could kludge something with a transformer but that kind of flies in the face of the direction of the technology.

Have you looked at the specs of the titan? Please correct me if wrong but it should be able to charge the truck. With 2kw pv input and the 30amp rv plug. My goal would be to camp for few day at a site and gain range while still running all the gear I would need. I have a yeti and I like it but there no comparison between the two. Plus I would always leave with the 6kw battery topped off. Trust me when I say I believe I'm out of my depth. My field of study and professionalism is it security not electrical engineering. My interest is to accomplish long-term camping and not drain my battery pack. I look forward to your input, and am happy to find this thread. I've been working this nut alone for awhile. ?